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turbine a/r and egt's....

Old 05-12-07, 07:32 PM
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turbine a/r and egt's....

ok since there has been a good amount of talk about turbine housings lately, i would like get some numbers of egt's on different housings. keeping things safe is always good. so if anyone has egt numbers for t4's with .84 , 1.00, 1.15, 1.32, etc. post them up. i am going with a t04z and am looking at either a 1.00 or 1.15. i know there will be a responce trade off but for engine prolonging it is worth it imo.
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Old 05-14-07, 07:48 AM
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EGT that is useful is pre-turbine. I'm not sure how much affect backpressure has on the temperature.

tuning is key...there are always ways to get the EGT down.
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Old 05-14-07, 08:02 AM
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Larger a/r's do generally keep egts down but so does a rich tune, the leaner you get the more power you make and the hotter the egts. This is where water injection comes in my friend.
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Old 05-14-07, 09:55 PM
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I noticed that when going from my BNR setup to my 500R 1.0 w/4 inch dp setup my peak EGTs decreased quite a bit, esp in higher gears. I'm talking like 150 degrees F, from 1400 to 1250. The sensor is in the dp, 3-4 inches post-turbine.
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Old 05-14-07, 10:40 PM
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im assuming egt's also rise with higher boost?
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Old 05-14-07, 10:59 PM
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Originally Posted by dubulup View Post
EGT that is useful is pre-turbine. I'm not sure how much affect backpressure has on the temperature.

tuning is key...there are always ways to get the EGT down.

I concur with the foregoing. More specifically, backpressure does raise the EGT as part of the adiabatic process (just as compression on the intake charge does). Expansion of the gases as they pass through the turbine will result in lower post turbine EGT's which are directly related to differential pressure. (In addition there are other heat losses through conduction, radiation, etc..)

The turbine, therefore, recovers some of the heat energy to drive the compressor. To be most useful for tuning, pre-turbine is indicated; with the preferred location of the thermocouple probe being in the exhaust port--or as close as you can get to it.
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Old 05-15-07, 07:04 AM
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EGT and EMP (exhaust manifold backpressure) are very related as has been mentioned.

both of the above also relate to AFR and tuning.

during the various (5) iterations of my twin TO4 setup i traveled from 45-50 psi EMP to 17-18 psi at one bar.

consider:

if you have alot of backpressure what happens to all the exhaust volume that doesn't get out of the pre turbo manifolding? guess where a bunch of it end up.

Polluting the next intake charge.

that's the absolute worst thing you can have entering a new charge.

it is hot. it has little oxygen.

gasoline auto ignites around 580-600 degrees f. the EGT is around 1500 or so. since there is a fractional amount and the incoming charge is much less we generally don't have autoignition.

generally but not always. 'know anyone that has lost an engine?

how much EMP do YOU have? just get a pressure sensor.... 0-100 psi converting to 0-5 volts, weld a bung into your pre turbo exhaust manifold, buy some Stainless Steel brake line, around 2-3 ft will do, hook it into one of your auxiliaries and get logging.

if i hadn't have done that i would still be running the turbo configuration offered by my turbo shop and wondering why my motor wasn't happy. (BTW, i run two 3 inch downpipes.)

my EGT's at around 500-600 hp at 18 psi on pump and methanol are 1200 degrees preturbo w no knock and 20 psi EMP.

all inter-related. all important for a happy motor... mine has 8000 miles on it and is still gaining compression.

howard coleman
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Old 05-15-07, 08:00 AM
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so what exactly was the setup before and after to make such a drastic change in manifold pressure?
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Old 05-15-07, 12:42 PM
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Originally Posted by smg944 View Post
so what exactly was the setup before and after to make such a drastic change in manifold pressure?
Usually a change in turbine trim and turbine A/R will get your backpressure where you want it. At 1.7 bar boost my T66 makes 2.1 bar backpressure. Thats a T66 with Q-trim turbine and 1.15 A/R.
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Old 05-15-07, 03:41 PM
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Originally Posted by smg944 View Post
so what exactly was the setup before and after to make such a drastic change in manifold pressure?
the manifold pressure ref.= exhaust manifold

howard coleman changed the A/R of the turbine housings.
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Old 05-15-07, 09:18 PM
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oh ok, also how much of a difference is the dp reading vs. pre manifold egt? i did some seaching and found that it is more accurate pre manifold. i was wondering what the threshold would be after turbo ( downpipe reading ).
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Old 05-15-07, 09:29 PM
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i have digitally logged (Datalogit/Power FC) pre turbo and post turbo egts. my plan was to figure out the differential and move my egts to post turbo.

i found that the relationship greatly varied based on rpm and load. at the top of my runs i noticed an approx 300 degree F difference.

based on my interest in knowing egts at all spots on the grid i retained my pre turbo egt location.

given my low egts due to methanol ( around 1200 F) my probes look real happy so i am not worried about damaging my turbos.

BTW, in addition to changing my A/Rs i changed my turbine wheel size to lower my EMP...

hc
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Old 05-16-07, 10:41 AM
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Originally Posted by GoodfellaFD3S View Post
I noticed that when going from my BNR setup to my 500R 1.0 w/4 inch dp setup my peak EGTs decreased quite a bit, esp in higher gears. I'm talking like 150 degrees F, from 1400 to 1250. The sensor is in the dp, 3-4 inches post-turbine.
I think an elephant's hiding in the corner with this. When you went single, you also changed from the twins' integrated wastegate to an external. Once the WG opens, some of the exhaust bypasses your EGT sensor with the single setup.
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Old 05-16-07, 03:02 PM
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Originally Posted by Eggie View Post
I think an elephant's hiding in the corner with this. When you went single, you also changed from the twins' integrated wastegate to an external. Once the WG opens, some of the exhaust bypasses your EGT sensor with the single setup.

Thats a good point. Plus I think he is running a 4" downpipe and exhaust which will let heat dissapate quicker.

R.K.
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